test(web): pin the remaining markdown fixture's event times

Master stabilized two of the three hand-built markdown fixtures by spacing
their event times, so the stats line's LLM segment stops depending on how fast
the replay ran. `markdown-images` was left on the old shape and kept failing
for exactly that reason — a different test each run, always the same one-line
difference.

Pin it the same way and record the segment its golden now always shows. This
supersedes the normalizer that dropped those segments outright, reverted here:
pinning the fixture keeps a real part of the page in the goldens instead of
hiding it from every one of them, and master's two goldens already record it.

apps/web/tests/snapshots/code-mode-round/ui.expected.md

@@ -36,7 +36,7 @@
   - img
 - button "Branch into a new conversation":
   - img
-- text: {{clock}} Ran for {{duration}} TTFT {{duration}}
+- text: {{clock}} Ran for {{duration}} TTFT {{duration}} {{throughput}} tok/s
 - textbox "Message the agent"
 - button "Commands":
   - img
@@ -46,4 +46,4 @@
   - img
 - button "7% of context used"
 - button "Send message" [disabled]
-- text: 1 turns · 2 steps TTFT avg {{duration}} Cache hit 52% Input 17.2K tok · Output 252 tok
+- text: 1 turns · 2 steps LLM {{duration}} · Tool call {{duration}} TTFT avg {{duration}} · {{throughput}} tok/s Cache hit 52% Input 17.2K tok · Output 252 tok